1. Field of the Invention
The present invention relates generally to an improved tunnel track interface for use with air-powered conveyor systems, and more particularly to an improved air tunnel track that interfaces the output of a can testing system with an air-powered conveyor system to increase the operation speed of the entire system.
2. Description of the Background Art
The LT-16-SM light tester is a self-contained electrical mechanical machine manufactured by Randolph Machinery Operations (a division of Alcoa Packaging Machinery, Inc.) to perform high speed automatic inspection of cans for defects in the flange and wall which could cause the cans to leak. The light tester checks for flange cracks and body holes by shining a light at a known 15 frequency inside the can as the cans are transferred along a main carrier wheel. Light sensing arrays are mounted on the carrier wheel so that only light passing through the cans is detectable. If light from the cans is detected, the sensing arrays are switched to a state that triggers the reject receiver causing the can to be rejected. Meanwhile, a discharge mechanism separates good cans from bad cans by transferring acceptable cans from a transfer point on the carrier wheel to a discharge transfer wheel assembly that feeds a conventional conveyor system. The light tester is capable of testing cans at speeds over 3,000 cans per minute (CPM).
A problem, however, occurring with the LT-16 light tester, and other systems utilizing similar discharge features, is that the testers are incapable of operating at full capacity without the cans jamming the tester. As a matter of fact, the system must typically be run at half speed in order to ensure against jamming. If the system is operated at too high a speed the cans have a tendency to "jam" at the discharge chute as the conveyors are fed.
One reason jamming occurs is that conventional chain driven conveyor systems are unreliable, inefficient, and slower. Accordingly, the light tester's speed must be decreased to synchronize it with the chain drive conveyor speed. On the other hand, air-powered conveyor systems, such as the dual plenum design disclosed by the inventor in U.S. Pat. No. 5,037,244, are capable of transporting cans through the conveyor system from one station to another at speeds comparable to the can tester, i.e., at a full line speed of approximately 3,600 CPM. Unfortunately, however, the light tester is also susceptible to jamming with the air-powered conveyor system when operated at speeds exceeding half capacity because of the path the can travels from the discharge assembly.
The dual plenum air-powered conveyor system disclosed in U.S. Pat. No. 5,037,244 comprises two U-shaped guide members, or inverted channels, in parallel and similar U-shaped jet plates that fit individually into the respective guide members to form air chambers or plenums therebetween. A plurality of spaced louver punches or air inlets are provided in the jet plate so that air supplied to the plenums by an outside source is fed into the can conveyance path to move the cans. Although the above noted air-powered conveyor systems are capable of running at 3,600 CPM they are presently incompatible for receiving cans from the light tester at full capacity. When the cans are released from the discharge chute they oscillate or bounce down the path slowing down subsequent cans. However, if the system is operated at slower speeds, such as 1,600CPM, the cans are able to settle into a straight path so as to prevent jamming. Consequently, even though both systems in isolation are capable of running at over 3,000CPM, in operation the present dynamics of the combination do not allow full capacity operation. The operator must therefore choose between running the risk of jamming which necessitates shutting the tester down or operating at less than full capacity. In either event, a loss of time and money results.
Therefore, as a result of the above-noted there exist a need for an interface device for communicating the light tester with conveyor systems in a way that allows the light testing system to operate at full capacity. The present invention satisfies this need by providing an air tunnel track attachment that generally interfaces the light tester with an air-powered conveyor system increasing the discharge speed of the cans so that the light tester and conveyor system may be operated near full capacity.